Field of the Invention
The present disclosure relates to a control device for an internal combustion engine.
Discussion of the Background
In the past, as a control device of this type of internal combustion engine, a control device disclosed in Japanese Unexamined Patent Application Publication No. 2009-293600, for example, has been known. In this internal combustion engine, a low-octane fuel and a high-octane fuel whose octane number is higher than the octane number of the low-octane fuel are used in combination as fuel, and the low-octane fuel is injected into a cylinder from a first fuel injection valve and the high-octane fuel is injected into an inlet port from a second fuel injection valve. Moreover, the low-octane fuel and the high-octane fuel are generated by separating the fuel stored in a fuel tank by a separator. Furthermore, in this existing control device, in order to suppress knocking of the internal combustion engine, a required octane number of the internal combustion engine is set and, based on the set required octane number, the injection quantities of fuel to be injected by the first and second fuel injection valves are controlled.
In addition, when knocking of the internal combustion engine is detected, high-octane fuel increase control by which the ratio of the supply of the high-octane fuel to the quantity of fuel which is supplied to the inside of the cylinder is increased is first performed. In the high-octane fuel increase control, the ratio of the supply of the high-octane fuel (hereinafter referred to as the “high-octane fuel ratio”) is increased to a maximum value commensurate with the detected knock intensity. Moreover, if knocking of the internal combustion engine is still occurring even when this high-octane fuel increase control is performed, ignition retardation control by which a correction to retard ignition timing of a spark plug of the internal combustion engine is made is performed. As described above, in this existing control device, by preferentially performing the high-octane fuel increase control before the ignition retardation control when knocking of the internal combustion engine is detected, a reduction in fuel economy of the internal combustion engine is suppressed with knocking of the internal combustion engine being suppressed.